Introduction

This package provides a "profile" based approach to generate ETags, and an evaluator to deal with Http Conditional Requests, for your Laravel application.

ETags Examples

Generate

use Aedart\ETags\Facades\Generator;

// Generate an ETag for strong comparison, of content
$etag = Generator::makeStrong($content);

echo (string) $etag; // "4720b076892bb2fb65e75af902273c73a2967e4a"

Or to generate ETags that are flagged as "weak" (for weak comparison)

$etag = Generator::makeWeak($content);

echo (string) $etag; // W/"0815"

Parsing

To parse ETags from Http headers, you can use the parse() method. It returns a collection of ETag instances.

// E.g. If-None-Match: W/"0815", W/"0816", W/"0817"
$collection = Generator::parse($request->header('If-None-Match'));  

foreach ($collection as $etag) {
    echo (string) $etag;
}

Compare

ETags can also be matched against each other, in accordance with RFC9110.

Using Collection

// Etags from Http Header
$collection = Generator::parse($request->header('If-Match')); // E.g. 'W/"0815"' 

// Other Etag for your resource
$etag = Generator::makeWeak($content); // E.g. W/"0815"

// Compare etags against resource's etag
echo $collection->contains($etag, true); // false - strong comparison
echo $collection->contains($etag);       // true - weak comparison

Using Etag instance

You can also compare individual ETag instances, using the matches() method.

$etagA = Generator::parseSingle('W/"0815"');
$etagB = Generator::parseSingle('W/"0815"');

echo $etagA->matches($etagB, true); // false - strong comparison
echo $etagA->matches($etagB);       // true - weak comparison

Evaluate Http Preconditions Examples

The Evaluator component is able to process the incoming request against all the defined RFC9110 preconditions, in accordance with specified evaluation precedence. Depending on the precondition requested, if it passes or fails, the request can either proceed or it will be aborted using customisable Http Exceptions. Your Laravel application should do the rest, whenever the request is aborted.

use Aedart\ETags\Preconditions\Evaluator;
use Aedart\ETags\Preconditions\Resources\GenericResource;

// Process If-Match, If-None-Match, If-Modified-Since... etc
// Depending on condition's pass/fail, the request can be aborted via
// an appropriate Http Exception, or proceed to your logic...
$resource = Evaluator::make($request)
    ->evaluate(new GenericResource(
        data: $model,
        etag: $model->getStrongEtag(),
        lastModifiedDate: $model->updated_at
    ));

To summarise, the following preconditions are supported:

• If-Match
• If-None-Match
• If-Modified-Since
• If-Unmodified-Since
• If-Range

The Evaluator also supports adding your own custom preconditions to be evaluated, should you need such.

Onward

For additional examples, installation guide and more, please continue reading the documentation.